Air knife



22, 1967 R. P. MAHONEY 3,336,899

AIR KNIFE Filed Oct 21, 1963 I NVENTOR United States Patent f 3,336,899AIR KNIFE Ralph P. Mahoney, Beloit, Wis., assignor to BeloitCorporation, Beloit, Wis., a corporation of Wisconsin Filed Oct. 21,1963, Ser. No. 317,669

5 Claims. (Cl. 118-63) ABSTRACT OF THE DISCLOSURE A paper web coatingmechanism employing an air knife wherein the air jet engages anadjustable deflector plate having a downwardly facing surface andinterposed be tween the air jet and paper web.

The present invention relates to improvements in mechanism for coatingtravelling webs and more particularly to an improved air knife coaterfor coating a paper web.

The invention provides a coating mechanism including a backing rollsupporting a travelling web with coating applying means applying acoating to the exposedsurface of the web and an air knife for smoothingand removing excess coating including an air jet directed toward thesurface of the oncoming travelling web on the uprunning side of thebacking roll and a deflector plate having a downwardly facing surfaceinterposed in the stream of air from the jet deflecting the airdownwardly and at an increased angle toward the oncoming coated websurface with the angle of the plate being adjustable.

An object of the invention is to provide an improved air knife coaterwith a mechanism for reducing the coating spray at the outgoing side ofthe knife and reducing or eliminating the need for coating spraycollecting apparatus and reducing the inherent disadvantages of residualcoating spray which travels in the air and covers adjacent machineryparts.

A further object of the invention is to provide an improved air knifecoater wherein the air knife lips stay cleaner and operate at continuedoptimum performance.

A still further object of the invention is to provide an air knifecoater wherein the air flow direction can be changed without requiringadjustment of the air knife.

A still further object of the invention is to provide an air knifecoater which can be operated at a fixed distance from the backing rolland travelling web and wherein there is less danger of damaging the airknife.

Yet another object of the invention is to provide an air knife coaterwhich is easier to clean and keep clean.

Other objects, advantages and features will become more apparent withthe teaching of the principles of the present invention in connectionwith the disclosure of the preferred embodiments thereof in thespecification, claims and drawings, in which:

The figure of the drawing illustrates schematically a coating mechanismembodying an air knife coater constructed and operating in accordancewith the principles of the present invention.

A travelling paper web W moves into the coating mechanism at a constantspeed and coating is applied to its lower surface by a coatingapplicator roll 11. The coating applicator roll runs partially submergedin a coating pan 12 to carry a layer of coating up against the lowersurface of the web W. As will be appreciated by those versed in the artcoating may be applied to the web by various means.

The coated web travels onto a backing roll and on the uprunning side ofthe roll is positioned an air knife including an air jet 13 directing astream of air 14 against the coated surface of the web. In accordancewith known operation of air knife coaters, the stream of high velocityair engages the coated surface of the web removing ex- 3,336,899Patented Aug. 22, 1967 cess coating and smoothing the coating whichpasses onwardly with the travelling web W.

The removed excess coating runs downwardly into a save-all pan 17 and iscarried away and may be transferred back to the main coating pan 12.

In air jet coating because of the velocity of the travelling web and thehigh velocity of the stream of air, with the coating tending to bethrown centrifugally outwardly, a spray or mist of coating normallydevelops on the outgoing side of the nozzle 13 of the air knife. Variousmeans have been attempted to reduce this mist including devices forcollecting and filtering the mist from the air. This mist will also tendto coat the air knife surfaces and the lips or edges of the knife ornozzle 13 will tend to become coated from coating being thrownoutwardly.

In accordance with the present invention means are provided for beinginterposed in the air stream 14 and deflecting the stream downwardly. Adeflector plate 15 is mounted above the air knife nozzle 13 with itsfree edge extending into the air stream 14 and with its lower surfacedeflecting the air stream downwardly at an increased angle with respectto the oncoming surface of the Web W. This lower surface of the plate 15changes the angle of the air jet and its effect with respect to theoncoming web surface, and air flow after it engages or impinges the webmust flow downwardly after contact. This reduces the mist caused by theair currents which normally form by escaping air and prevents thetravelling of a mist upwardly onto the freshly finished coated surfaceof the web after it passes the air jet thereby improving the quality ofthe coating on the paper surface. The fine particles of mist whichnormally escape become partially dried While travelling in the air andwhen they engage on the surface of the finished coated web they do notmelt or merge into the surface but provide surface imperfection. This iseliminated with the present arrangement.

In operation coating is applied to the undersurface of the travellingweb W and the air jet from the air nozzle 13 as deflected by theoverhead plate 15 engages the freshly coated surface removing the excesscoating to run down into the save-all pan 17 and the finished coatedsurface continues on with the web W. For optimum operation adjustment ofthe deflector plate 15 is possible such as by provision of an adjustmentscrew 16 mounted at the top of the nozzle. This can be used as a partialsupport for the deflector 15. If desired additional adjustment means canbe provided for adjusting the position of the plate 15 parallel to itsplane and toward or away from the surface of the travelling web W.

This adjustment mechanism can be provided by various means such asadjustment screws which need not be shown in detail, but instead areillustrated schematically by the arrowed :line 18.

With the arrangement shown the nozzle 13 can be kept a substantialdistance from the travelling web W and adjustment of the direction ofthe air flow can be made without adjustment of the jet reducing thedanger of damaging the air knife during adjustment or installation.

Thus it will be seen that I have provided an improved coatingarrangement and method which meet the objectives and advantages aboveset forth. The structure is relatively simple in operation andconstruction and can be utilized in existing coater or in new coaterswith a minimum of expense and space requirement.

The drawings and specification present a detailed disclosure of thepreferred embodiments of the invention, and it is to be understood thatthe invention is not limited to the specific forms disclosed, but coversall modifications, changes and alternative constructions and methodsfalling within the scope of the principles taught by the invention.

I claim as my invention:

1. A coating mechanism comprising in combination,

a backing roll supporting a travelling web, coating applying meansapplying coating to the surface of the Web,

an air knife for smoothing and removing excess coating including aprimary coating smoothing air jet directed toward the surface of thetravelling web on the backing roll,

a deflector plate having a surface interposed in the stream of air fromthe jet deflecting the air toward the oncoming coated web surface, andmeans for adjusting the angle of said plate relative to said jet.

2. A coating mechanism comprising in combination,

a backing roll supporting a travelling web,

coating applying means applying coating to the surface of the web,

an air knife for smoothing and removing excess coating including aprimary coating smoothing an air jet directed toward the surface of thetravelling web on the backing roll,

and a deflector member having a surface interposed in the stream of airfrom the jet deflecting the air toward the oncoming coated web surface.

3. In combination with a coating mechanism having means for applying alayer of coating to the surface of a continuously travelling web,

a primary coating smoothing air knife coater having an air jet directinga stream of air against the coated surface,

and means defiectively engaging the air stream between the web and jetand changing the direction of the stream of air relative to the web.

4. A coating mechanism comprising in combination,

a backing roll having a surface supporting a travelling web,

coating applying means applying coating to the surface of the web,

an air knife for smoothing and removing excess coating including aprimary coating smoothing air jet directed toward the surface of thetravelling web on the uprunning side of the roll,

a deflector plate mounted above said air jet having an edge projectingbeyond the jet with a downwardly facing surface projecting into the airstream and deflecting air downwardly,

and means on the knife for adjustably changing the angle of the platerelative to the jet.

5. A coating mechanism comprising in combination,

a backing roll having an outer cylindrical surface for supporting atravelling paper web,

a coating applicator roll positioned in advance of the backing roll forapplying a layer of coating to the exposed surface of the web,

a coating pan positioned with the coating roll partially submergedtherein for carrying coating onto the web surface,

a primary coating smoothing air jet positioned on the uprunning side ofthe backing roll directing a stream of air onto the coated surface ofthe web and directed at an angle with respect to the web toward theoncoming web for removing excess coating and smoothing the remainingcoating on the web,

a deflector plate mounted on the air jet having an edge extending beyondthe jet with a downwardly facing surface interposed in the stream of airfrom the jet deflecting the air stream downwardly and directly air flowdownwardly after impingement contact with the coated surface of the web,

and adjustment means on said air jet for positioning the angle of saidplate relative to the air jet.

References Cited UNITED STATES PATENTS MORRIS KAPLAN, Primary Examiner.

1. A COATING MECHANISM COMPRISING IN COMBINATION, A BACKING ROLLSUPPORTING A TRAVELLING WEB, COATING APPLYING MEANS APPLYING COATING TOTHE SURFACE OF THE WEB, AN AIR KNIFE FOR SMOOTHING AND REMOVING EXCESSCOATING INCLUDING A PRIMARY COATING SMOOTHING AIR JET DIRECTED TOWARDTHE SURFACE OF THE TRAVELLING WEB ON THE BACKING ROLL, A DEFLECTOR PLATEHAVING A SURFACE INTERPOSED IN THE STREAM OF AIR FROM THE JET DEFLECTINGTHE AIR TOWARD THE ONCOMING COATED WEB SURFACE AND MEANS FOR ADJUSTINGTHE ANGLE OF SAID PLATE RELATIVE TO SAID JET.